Experience in the P-38 before the 479th left states was a key to the 479th's success in the ETO when they got shipped over seas.
I've been away from this subject for awhile - apologize for excavating a dead horse.
I devoted a significant amount of time digging into P-38 ETO history for my new book "P-51 Mustang; NAA's Bastard Stepchild that Saved the 8th AF" - (forgive the hyperbole).
First, a mild rebuttal on the comment >experience was the key for the 479th. IMO it was Zemke's leadership as the surge in VC's for the 479th was after he took over in August, 1944 - particularly in late September just before conversion to P-51. A comparison could be the 55th FG which had as much training as the 479th 'in type'.
The resolution of issues with the engines/aftercooler and oil cooler embodied in the early J through mid block J-15, including introduction of second generator to provide cockpit cooling as well as simplified controls, marked the beginning of the P-38 as a fighter pilot's airplane in combat with LW at high altitude ETO conditions. Neither the 479t nor 20th, 55th and 364th ever flew the J-25 with dive flap and boosted ailerons - only the 9th AF got those in October/November and the 15th only got P-38Js in MTO in June/J-25 in November, 1944. Comment here - the 332nd 'Red Tails' outscored each of the VERY experienced 1st, 14th and 82nd FG after they (332nd) converted to Mustangs in the MTO.
For the 8th AF P-38 combat record, the evaluation of USAF 85 VCs to 'probable air to air losses' documented by MACRs, point to about 1.6:1 air to air for all four groups. If you separate the 479th FG, the other 3 FGs were closer to 1:1.
There were six fighter Aces in 479th. Of the 6 (Zemke, Jeffrey, Gleason, Olds, Candelaria and Creighton) ONLY Olds managed to get five in the P-38 in four plus months of operations.
The number of air aces that got five or more in P-38H/J in ETO are barely a handful. The top P-38J ace (Morris 7.33 20th FG) was shot down by an Me 410 after 7 months in combat ops. He was also unique as the first 8th AF pilot to score 4 on one mission.
The P-38J flown by the 20th, 55th, 364th and 479th also had the highest loss per VC ratio for airfield strafing. Big target, two vulnerable cooling systems - each prone to quick fires when hit by explosive shells. For the ETO the top VC to strafing loss ratio was the P-51. (IMO that was because the range and reduced target profile enabled the P-51 to strike more less defended airfields early on before the LW upgunned all airfields with light 20mm flak.)
That said, my father's group (355th FG) did not lose Any aces to air to air (of 21) but lost five shot down by flak (one rescued) and one stuck in mud attempting a rescue.
As to '440 mph' top speed for P-38L. No AAF flight test substantiates the Lockheed claims for anything above 414+ mph with combat load out. I'm not saying the L could Not exceed 414 with the final engine/cooling capability - but the fat P-38 wing and overall cumulative parasite drag caused a signifcant onset Mach well short of similar drag rise speeds in a P-51.